chore: improve debugging for no subnets error in task run

internal/pkg/cli/task_run.go

@@ -438,6 +438,10 @@ func (o *runTaskOpts) runTask() ([]*task.Task, error) {
 	o.spinner.Start(fmt.Sprintf("Waiting for %s to be running for %s.", english.Plural(o.count, "task", ""), o.groupName))
 	tasks, err := o.runner.Run()
 	if err != nil {
+		if errors.Is(err, task.ErrNoSubnetFound) {
+			log.Warningf("Subnets need to be tagged with %s and %s. Are your subnets tagged?\n", deploy.AppTagKey, deploy.EnvTagKey)
+		}
+
 		o.spinner.Stop(log.Serrorf("Failed to run %s.\n\n", o.groupName))
 		return nil, fmt.Errorf("run task %s: %w", o.groupName, err)
 	}

internal/pkg/task/config_runner.go

@@ -53,7 +53,7 @@ func (r *NetworkConfigRunner) Run() ([]*Task, error) {
 			return nil, fmt.Errorf(fmtErrDefaultSubnets, err)
 		}
 		if len(subnets) == 0 {
-			return nil, errNoSubnetFound
+			return nil, ErrNoSubnetFound
 		}
 
 		r.Subnets = subnets

internal/pkg/task/env_runner.go

@@ -60,7 +60,7 @@ func (r *EnvRunner) Run() ([]*Task, error) {
 		return nil, fmt.Errorf(fmtErrPublicSubnetsFromEnv, r.Env, err)
 	}
 	if len(subnets) == 0 {
-		return nil, errNoSubnetFound
+		return nil, ErrNoSubnetFound
 	}
 
 	// Use only environment security group https://github.com/aws/copilot-cli/issues/1882.

internal/pkg/task/env_runner_test.go

@@ -83,7 +83,7 @@ func TestEnvRunner_Run(t *testing.T) {
 				m.EXPECT().SecurityGroups(gomock.Any()).AnyTimes()
 			},
 			mockStarter: mockStarterNotRun,
-			wantedError: errNoSubnetFound,
+			wantedError: ErrNoSubnetFound,
 		},
 		"failed to get security groups": {
 			MockClusterGetter: MockClusterGetter,

internal/pkg/task/errors.go

@@ -8,8 +8,9 @@ import (
 	"fmt"
 )
 
+// Errors returned while trying to run a task.
 var (
-	errNoSubnetFound = errors.New("no subnets found")
+	ErrNoSubnetFound = errors.New("no subnets found")
 
 	errVPCGetterNil     = errors.New("vpc getter is not set")
 	errClusterGetterNil = errors.New("cluster getter is not set")